Solid-state imaging device, method for driving solid-state imaging device, and electronic apparatus

Abstract

A solid-state imaging device, a method for driving the solid-state imaging device, and an electronic apparatus capable of suppressing occurrence of motion distortion while realizing widening of dynamic range and in turn realizing a higher image quality are provided. Each pixel includes a photo diode PD which accumulates a charge generated by photo-electric conversion in an accumulation period, a transfer transistor capable of transferring the accumulated charge in a transfer period, a floating diffusion FD to which the charge accumulated in the photo diode PD is transferred, a source-follower transistor which converts the charge of the floating diffusion FD to a voltage signal in accordance with the charge quantity, and a capacity changing portion capable of changing the capacity of the floating diffusion FD in accordance with a capacity changing signal, the capacity of the floating diffusion FD being changed by the capacity changing portion in a predetermined period in one readout period with respect to the accumulation period and a conversion gain being switched in this one readout period.

The invention claimed is: 
     
       1. A solid-state imaging device comprising a pixel portion in which pixels are arranged, wherein
 the pixel portion includes a first wiring which is formed over a plurality of pixels in the same column or row in order to connect floating diffusions of at least two adjacent pixels, and 
 each pixel includes 
 a photo-electric conversion element which accumulates a charge generated by photo-electric conversion in an accumulation period, 
 a transfer element capable of transferring the charge accumulated in the photo-electric conversion element in a transfer period, 
 a floating diffusion to which the charge accumulated in the photo-electric conversion element is transferred through the transfer element, 
 a source-follower element which converts the charge of the floating diffusion to a voltage signal by a gain in accordance with the charge quantity, and 
 a capacity changing portion capable of changing the capacity of the floating diffusion in accordance with a capacity changing signal, 
 a second wiring connecting the floating diffusion to the first wiring, and 
 a connection node to the second wiring in the first wiring, wherein 
 the capacity of the floating diffusion is changed by the capacity changing portion in a predetermined period in one readout period with respect to the accumulation period and a conversion gain is switched in the one readout period, and wherein 
 the capacity changing portion 
 includes a binning switch which is connected to the first wiring between the connection nodes in at least two adjacent the pixels and is selectively turned on or off in accordance with the capacity changing signal and 
 switches the number of floating diffusions to be connected and switches the conversion gain of the floating diffusion of the pixel to be read out. 
 
     
     
       2. A solid-state imaging device as set forth in  claim 1 , wherein all of a plurality of pixels which are connected through the binning switches share a reset element which discharges the charges in the floating diffusions in a reset period. 
     
     
       3. A solid-state imaging device as set forth in  claim 1 , wherein the capacity changing portion includes
 a first binning switch which is connected to the first wiring between the connection nodes of two adjacent the pixels and is selectively turned on or off in accordance with a first capacity changing signal and 
 a second binning switch which is connected the first wiring and the floating diffusion which is a wiring nearer the transfer element side than the first binning switch and is selectively turned on or off in accordance with a second capacity changing signal. 
 
     
     
       4. A solid-state imaging device as set forth in  claim 3 , wherein the capacity changing portion has an overflow gate which is connected to the first binning switch and discharges an overflowing charge from the floating diffusion. 
     
     
       5. A solid-state imaging device as set forth in  claim 1 , further comprising
 a readout portion for reading out a pixel signal from the pixel portion, wherein 
 the readout portion performs, in one the readout period, at least one of 
 a first conversion gain mode reading operation for reading out a pixel signal by a first conversion gain in accordance with a first capacity which is set by the capacity changing portion and 
 a second conversion gain mode reading operation for reading out a pixel signal by a second conversion gain in accordance with a second capacity which is set by the capacity changing portion. 
 
     
     
       6. A solid-state imaging device as set forth in  claim 5 , further comprising
 a reset element which discharges the charge of the floating diffusion in a reset period, wherein 
 the readout portion performs the first conversion gain mode reading operation and the second conversion gain mode reading operation in the readout period operation following the reset period. 
 
     
     
       7. A solid-state imaging device as set forth in  claim 6 , wherein the readout portion performs at least one of the first conversion gain mode reading operation and the second conversion gain mode reading operation in a readout period after at least one transfer period which starts after the readout period following the reset period. 
     
     
       8. A solid-state imaging device as set forth in  claim 5 , wherein the second capacity is larger than the first capacity. 
     
     
       9. A solid-state imaging device as set forth in  claim 1 , wherein the pixel portion has a pixel shared structure where one floating diffusion is shared by a plurality of the photo-electric conversion elements and the transfer elements. 
     
     
       10. A solid-state imaging device as set forth in  claim 1 , wherein the solid-state imaging device is a front-surface irradiation type or back-surface irradiation type. 
     
     
       11. A method for driving a solid-state imaging device having a pixel portion in which pixels are arranged, wherein
 the pixel portion includes a first wiring which is formed over a plurality of pixels in the same column or row in order to connect floating diffusions of at least two adjacent pixels, and 
 each pixel includes 
 a photo-electric conversion element which accumulates a charge generated by photo-electric conversion in an accumulation period, 
 a transfer element capable of transferring the charge accumulated in the photo-electric conversion element in a transfer period, 
 a floating diffusion to which the charge accumulated in the photo-electric conversion element is transferred through the transfer element, 
 a source-follower element which converts the charge of the floating diffusion to a voltage signal by a gain in accordance with the charge quantity, and 
 a capacity changing portion capable of changing the capacity of the floating diffusion in accordance with a capacity changing signal, 
 a second wiring connecting the floating diffusion to the first wiring, and 
 a connection node to the second wiring in the first wiring, 
 comprising changing the capacity of the floating diffusion by the capacity changing portion in the predetermined period in one readout period with respect to the accumulation period and switching a conversion gain in the one readout period, 
 the method for driving a solid-state imaging device comprising 
 forming the capacity changing portion
 by forming the first wiring corresponding to the pixel arrangement of the pixel portion, 
 by connecting the floating diffusions of at least two adjacent the pixels to the first wiring by the second wirings, and 
 by connecting a binning switch to the first wiring between the connection nodes in at least two adjacent pixels, and 
 
 selectively turning the binning switch on or off in accordance with the capacity changing signal to switch the number of floating diffusions connected and switch the conversion gains of the floating diffusions of the read out pixels. 
 
     
     
       12. An electronic apparatus comprising
 a solid-state imaging device which includes a pixel portion in which pixels are arranged and 
 an optical system which forms an object image at the solid-state imaging device, wherein 
 the pixel portion of the solid-state imaging device includes a first wiring which is formed over a plurality of pixels in the same column or row in order to connect floating diffusions of at least two adjacent pixels, and 
 each pixel of the solid-state imaging device includes 
 a photo-electric conversion element which accumulates a charge generated by photo-electric conversion in an accumulation period, 
 a transfer element capable of transferring the charge accumulated in the photo-electric conversion element in a transfer period, 
 a floating diffusion to which the charge accumulated in the photo-electric conversion element is transferred through the transfer element, 
 a source-follower element which converts the charge of the floating diffusion to a voltage signal by a gain in accordance with the charge quantity, and 
 a capacity changing portion capable of changing the capacity of the floating diffusion in accordance with a capacity changing signal, 
 a second wiring connecting the floating diffusion to the first wiring, and 
 a connection node to the second wiring in the first wiring, wherein 
 the capacity of the floating diffusion is changed by the capacity changing portion in a predetermined period in one readout period with respect to the accumulation period and a conversion gain is switched in the one readout period, and wherein 
 the capacity changing portion 
 includes a binning switch which is connected to the first wiring between the connection nodes in at least two adjacent the pixels and is selectively turned on or off in accordance with the capacity changing signal and 
 switches the number of floating diffusions to be connected and switches the conversion gain of the floating diffusion of the pixel to be read out.